Intrinsic repair of articular cartilage damage is unsatisfactory, largely due to its avascular natue and demanding physical environment. Hydrogels are attractive biomaterials for cartilage regeneration, as they can conform within complex chondral defects, adhere to and integrate with surrounding tissues, and encapsulate and direct stem cell differentiation. The aim of this study is to evaluate a novel hyaluronic acid hydrogel seeded with mesenchymal stem cells in a cartilage defect in a large animal model. We will specifically address two different approaches for cartilage restoration using this system: 1) direct fabrication of the engineered material in th cartilage defect, where differentiation and maturation is controlled by co-encapsulated growth factor- laden microspheres, and 2) implantation of an engineered construct that has been pre- matured ex vivo under defined conditions to attain cartilage-relevant mechanical and biochemical properties. Optimization of each approach will involve detailed analysis of cartilage properties after implantation using advanced mechanical and imaging modalities. If successful, this work has the potential to dramatically change the course of treatment of persons with significant cartilage injuries and osteoarthritic degeneration, and as such, would improve the lives of military personnel and society as a whole. PUBLIC HEALTH RELEVANCE: Intrinsic repair of articular cartilage damage is unsatisfactory, due to its avascular nature and demanding physical environment. Military personnel suffer from cartilage damage at a higher rate than the general population, restricting active duty and leading to the development of osteoarthritis (OA) and the need for total joint replacement. The aim of this study is to evaluate novel tissue engineered construct based on a hyaluronic acid hydrogel seeded with mesenchymal stem cells. We will determine the best route towards clinical efficacy, i.e., direct formation of the engineered material within the defect, or a process where tissues are matured in vitro and then implanted. This work will dramatically improve treatment options for the military population suffering from acute cartilage injury and those debilitated from the ravages of progressive OA.